Angiogenesis plays an important role in the pathogenesis of a number of disorders, including solid tumors and metastasis. The production of new blood vessels is essential for providing oxygen and nutrients for the growth and spread of a tumor, and therefore angiogenesis is a good target for cancer therapeutics.
Angiogenesis involves a family of proteins acting as angiogenic activators, including vascular endothelial growth factor (VEGF-A), VEGF-B, VEGF-C, VEGF-E, and their respective receptors (VEGFR-1, VEGFR-2, and VEGFR-3). VEGF-A, also referred to as VEGF or vascular permeability factor (VPF), exists in several isoforms that arise from alternative splicing of mRNA of a single VEGF gene, with VEGF165 being the most biologically relevant isoform.
Anti-VEGF antibodies have been shown to suppress the growth of tumor cells in vitro and in vivo. A humanized anti-VEGF monoclonal antibody, bevacizumab (AVASTIN) has been developed and approved in the United States as a cancer therapeutic.
The Notch signaling pathway is a universally conserved signal transduction system. It is involved in cell fate determination during development including embryonic pattern formation and post-embryonic tissue maintenance. In addition, Notch signaling has been identified as a critical factor in the maintenance of hematopoietic stem cells.
The Notch pathway has been linked to the pathogenesis of both hematologic and solid tumors and cancers. Numerous cellular functions and microenvironmental cues associated with tumorigenesis have been shown to be modulated by Notch pathway signaling, including cell proliferation, apoptosis, adhesion, and angiogenesis (Leong et al., 2006, Blood, 107:2223-2233). In addition, Notch receptors and/or Notch ligands have been shown to play potential oncogenic roles in a number of human cancers, including acute myelogenous leukemia, B cell chronic lymphocytic leukemia, Hodgkin lymphoma, multiple myeloma, T-cell acute lymphoblastic leukemia, brain cancer, breast cancer, cervical cancer, colon cancer, lung cancer, pancreatic cancer, prostate cancer, and skin cancer. (Leong et al., 2006, Blood, 107:2223-2233).
Delta-like 4 ligand (DLL4) is an important component of the Notch pathway and has been identified as a target for cancer therapy. DLL4 is a Notch ligand, characterized by an N-terminal domain, a Delta/Serrate/Lag-2 (DSL) domain and tandem EGF-like repeats within the extracellular domain. It has been reported that DLL4 is induced by VEGF and that DLL4 may act as a negative feedback regulator for vascular proliferation.
Anti-DLL4 antibodies have been shown to enhance angiogenic sprouting and branching which leads to non-productive angiogenesis and decreased tumor growth (Noguera-Troise et al., 2006, Nature, 444:1032-1037). In addition, an anti-DLL4 antibody, 21M18, has been shown to inhibit tumor growth and reduce the frequency of cancer stem cells in xenograft tumor models (Hoeg et al., 2009, Cell Stem Cell, 5:168-177; U.S. Pat. No. 7,750,124).
Although there have been significant strides in development of monoclonal antibodies for use in cancer treatments, there is still great potential for further improvements. One class of antibody molecules with the promise of enhanced potency and/or reduced side effects (e.g., toxicity) is bispecific antibodies.
Early bispecific molecules were mainly generated using chemical cross-linking of two antibodies, or were hybrid hybridomas or “quadromas”. One success of the quadroma format is triomabs, which are mouse/rat combinations that demonstrate a preferential species-specific heavy/light chain pairing. More recently, advances in antibody engineering have provided a wide variety of new antibody formats, including, but not limited to, tandem scFv (bi-scFv), diabodies, tandem diabodies (tetra-bodies), single chain diabodies, and dual variable domain antibodies.
It is one of the objectives of the present invention to provide improved molecules for cancer treatment, particularly bispecific antibodies that specifically bind human VEGF and human DLL4.